祭奠 

Pinyin: jìdiàn 
Meaning：Hold a memorial ceremony for
Sentence: The graves are decked with flowers.一个个的坟墓上都摆放着祭奠的鲜花。 

More: 

祭： 

Pinyin: zhài,jì
Meaning: Offer sacrifice
Radical: 示
Stokes: 11
Traditional: 祭
Common words/Phrase:
祭司 [jìsī] 【priest】
祭祖 [jìzǔ] 【ancestor worship】
祭坛 [jìtán] 【altar】
祭品 [jìpǐn] 【offering】

奠： 

Pinyin: sì
Meaning: Offer sacrifice to
Radical: 大
Stokes: 12
Traditional: 奠
Common words/Phrase:
奠定 [diàndìng] 【settle】 
奠基 [diànjī] 【lay a foundation】
奠基石 [diànjīshí] 【cornerstone】